Heat developable photographic copying materials



United States Patent "ice 3,523,795 HEAT DEVELOPABLE PI-IOTOGRAPHIC COPYING MATERIALS Kinji Ohkubo and Takao Masuda, Kanagawa, .lapan, assignors to Fuji Shashin Film Kabushlki Kaisha, Ashlara-Kani un, Kanagawa, apan l \lo Drawiig. Filed Dec. 22, 1965, Ser. No. 515,761 Claims priority, application Japan, Dec. 25, 1964, 39/ 73,005 Int. Cl. G03c 1/06, 1/48, 5/30 US. Cl. 96-66 16 Claims ABSTRACT OF THE DISCLOSURE This invention relates to a process of producing photographic images by thermal development and more particularly, to heat developable light sensitive silver halide photographic copying materials.

It is well known that many characteristics are required for copying materials. In general, processing of these copying materials by the dry or semi-dry method are preferred, because it has such advantages that the preparation of a processing solution is not necessary, and hands or clothes are not soiled.

According to the present invention there is provided a heat developable light sensitive material comprising a support bearing one or more layers of a colloidal binder containing at least (a) a light sensitive silver halide, (b) at least one thermolabile compound which is decomposed by heat to liberate the base, (6) at least one substance which yields water when heated, and (d) a silver halide developing agent.

Thermolabile compounds which decompose by heat to liberate the base which can be employed in the present invention are: oxalates of aliphatic amine, e.g., dicyclohexylamine oxalate; oxalates of aromatic amine, e.g., benzylamine oxalate; and oxalates of heterocyclic amine, e.g., piperidine oxalate and morpholine oxalate. In general, these monoamino oxalates are prepared by adding an aqueous or alcoholic solution of amine to an aqueous or alcohlic solution of oxalic acid in an excess equivalent. The salt compound precipitate, is removed by filtration, washed with solvent to remove excess reactants, filtered and dried.

When the above-mentioned oxalates of an amine are heated to their decomposition temperature, they are decomposed to produce carbon dioxide and amine in the amount sufficient to give the basicity required for the development. Monoamino oxalate is superior in its photographic properties and workability in preparing the amine salts, as compared with other organic acid salts (e.g., trichloroacetates). The decomposition temperatures of the thermolabile salts are as follows: dicyclohexylamine oxalate, ca. 120 C.; benzylamine oxalate, ca. 125 C.;

3,523,795 Patented Aug. 11, 1970 piperidine oxalate, ca. 105 C.; and morpholine oxalate, ca. 135 C.

As substances which yield water upon heating, there are used substances containing water of crystallization. Above all, metal salts of acetic acid are recommended considering the temperature at which water of crystallization is evolved and the adaptability to photographic emulsions. If sodium acetate trihydrate is ,used to this end, the weak alkalinity of sodium acetate itself accelerates reduction during storage of the raw materials, resulting in fog. However, magnesium acetate tetrahydrate, zinc acetate dihydrate, cadmium acetate dihydrate, lead acetate trihydrate and manganese acetate tetrahydrate can be favorably used. These compounds yield a part of the water of crystallization at a temperature less than 100 C. and the remaining water of crystallization is evolved at 100 C. The crystallization water evolving temperatures of the compounds as mentioned above as measured by diif rential thermal analysis are: magnesium acetate tetrahydrate, C. and 100 C.; zinc acetate dihydrate, 80 C. and 100 C.; cadmium acetate dihydrate, C. and 100 C.; lead acetate trihydrate, 50 C. and 100 C.; and manganese acetate tetrahydrate, 40 C., 55 C., C. and C.

Calcium acetate monohydrate and barium acetate monohydrate can also be used in the materials of the present invention.

If desired, two or more of these substances may be used simultaneously.

As the silver halide developing agents which can be employed in the present invention are unsubstituted dihydroxybenzene, unsubstitutued trihydroxybenzene, halogen substituted, lower alkyl (C substituted, and aryl substituted dihydroxybenzenes. Suitable examples of such compounds are hydroquinone, methylhydroquinone, chlorohydroquinone, bromohydroquinone, phenylhydroquinone, 2,5-di-tert-butylhydroquinone, catechol and pyrogallol. One or more of these compounds are used in the materials of the present invention, and if necessary, may be used together with l-phenyl-3-pyrazolidone. If 1- phenyl-3-pyrazolidone is used with another developing agent, development of fog is often reduced.

The foregoing thermolabile compounds which are decomposed by heat to liberate a base, substances which yield water upon heating and silver halide developing agent are mixed with a light sensitive silver halide emulsion, applied to a suitable support, e.g., paper, film and glass, and dried. A part of these compounds may be separately mixed with a light sensitive silver halide emulsion and colloidal binder solution, applied to a suitable support and dried. The order of application is arbitrary.

When the resultant photographic copying material, after exposure to light, is heated, for example, by passing it through two hot rollers or holding it between two hot plates, water is evolved from the compound which yields water by heating, whereby the medium is wetted, at the same time, the medium becomes basic by the decomposition of the thermolabile compound to liberate the base by heating, and the developing agent is activated, whereby an exposed part of the silver halide is developed.

In the method of the present invention, as mentioned above, the development of the photographic copying material exposed to light may be accomplished only by heating without using any liquid. After the development, it can be fixed or stabilized in the ordinary manner.

The present invention is further illustrated by the following examples:

EXAMPLE 1 Preparation of thermolabile monomino oxalates which are decomposed by heat to liberate a base:

(a) Dicyclohexylamine oxalate Fifty grams of oxalic acid is dissolved in 250 ml. of water, to which 50 ml. of dicyclohexylamine is added at room temperature with stirring. The resulting precipitate is filtered, washed with water three times and dried.

(b) Benzylamine oxalate Fifty grams of oxalic acid is dissolved in 250 ml. of water, to which 50 ml. of benzylamine is added at room temperature with stirring. The resulting precipitate is filtered, washed with water three times and dried.

( c) Piperidine oxalate A solution of piperidine in ethyl alcohol (40 g./100 ml.) is added to a solution of oxalic acid in ethyl alcohol (60 g./250 ml.) at room temperature with stirring. The resulting precipitate is filtered, washed with ethyl alcohol three times and then dried.

(d) Morpholine oxalate A solution of morpholine in ethyl alcohol (50 ml./ 100 ml.) is added to a solution of oxalic acid in ethyl alcohol (50 g./ 250 ml.) at room temperature with stirring. The resulting precipitate is filtered, washed with ethyl alcohol three times and dried.

EXAMPLE 2 A dispersion containing 100 g. of silver chloride emulsion (containing 0.015 mol of silver chloride and 11 g. of gelatin per 100 g.), 2 g. of hydroquinone, 10 g. of lead acetate trihydrate, 2.5 g. of dicyclohexylamine oxalate, suitable amounts of a color sensitizer, fog inhibitor, wetting agent and hardening agent, is coated on baryta paper and dried. The resultant material is exposed, and is heated at 140 C. for 10 seconds by the use of hot plates to obtain images.

' EXAMPLE 3 Two grams of hydroquinone, suitable amounts of a color sensitizer, fog inhibitor, wetting agent and hardening agent are added to 100 g. of the silver chloride emulsion described in Example 2, and the resulting dispersion is coated on a paper as underlayer. It is then coated with an overlayer containing 10 g. of gelatin, 30 g. of zinc acetate dihydrate, 7.5 g. of piperidine oxalate, suitable amounts of wetting agent and hardening agent. After exposure to light, the development is carried out by heating at 140 C. for 30 seconds.

EXAMPLE 4 A layer containing 5 g. of gelatin and 2 g. of hydro quinone is coated on 2.5 m? of paper as underlayer. Then, a layer containing 100 g. of the silver chloride emulsion described in Example 2, suitable amounts of a color sensitizer, fog inhibitor, wetting agent and hardening agent is overcoated as a middle layer. Furthermore, it is covered with an overlayer containing g. of gelatin, 30 g. of cadmium acetate dihydrate and 7.5 g. of morpholine oxaout by heating at 130 C. for 30 seconds.

EXAMPLE 5 Two grams of monochlorohydroquinone, g. of lead acetate trihydrate, suitable amounts of a color sensitizer, fog inhibitor, wetting agent and hardening agent are added to 100 g. of the silver chloride emulsion described in Example 2, and the resulting dispersion is coated on a baryta paper. It is then coated with an overlayer containing 7 g. of gelatin and 10 g. of morpholine oxalate. After exposure to light, the development is carried out by heating at 140 C. for 30 seconds.

EXAMPLE 6 One hundred grams of the silver chloride emulsion described in Example 2 is coated with suitable amounts of a color sensitizer, fog inhibitor, wetting agent and hardening agent on 2.5 m? of baryta paper. It is then coated with an overlayer containing 10 g. of gelatin, 2 g. of monomethylhydroquinone, 20 g. of lead acetate dihydrate, 10 g. of morpholine oxalate, suitable amounts of wetting agent and hardening agent. After exposure to light, the development is carried out by heating at 140 for 30 seconds.

EXAMPLE 7 The following dispersions are applied in order on 2.5 m? of baryta paper:

(a) An aqueous solution containing 5 g. of gelatin and 6 g. of morpholine oxalate,

(b) An aqueous solution containing 5 g. of gelatin, 20 g. of hydroquinone, and 0.03 g. of 1-phenyl-3-pyrazolidone,

(0) An aqueous suspension containing g. of silver chloride emulsion described in Example 2, and

(d) An aqueous solution containing 20 g. of lead acetate trihydrate and 10 g. of gelatin.

The resultant material is exposed to light, and is heated at C. for 30 seconds to obtain an image. When 1- phenyl-3-pyrazolidone is used in solution (b), the fog density is lower than in the case of using only hydroquinone.

The light sensitive material developed described in Examples 2-7 may be fixed or stabilized in a conventional manner.

What we claim is:

1. A heat developable light sensitive material comprising a support bearing at least one layer of a colloidal binder containing at least (a) a light sensitive silver halide, (b) at least one thermolabile monoamino oxalate which is decomposed by heat to liberate a base, (0) at least one hydrated metallic salt of acetic acid which yields water at a temperature lower than the decomposition temperature of said monoamino oxalate, and (d) a silver halide developing agent.

2. A material as claimed in claim 1 wherein a light sensitive silver halide is silver chloride.

3. A material as claimed in claim 1 wherein the oxalate is selected from the group consisting of oxalates of aliphatic amine, oxalates of aromatic amine, and oxalates of heterocyclic amine.

4. A material as claimed in claim 3 wherein the oxalate is dicyclohexylamine oxalate.

5. A material as claimed in claim 3 wherein the oxalate is benzylamine oxalate.

6. A material as claimed in claim 3 wherein the oxalate is piperidine oxalate.

7. A material as claimed in claim 3 wherein the oxalate is morpholine oxalate.

8. A material as claimed in claim 1 wherein said hydrated acetic acid salt is lead acetate trihydrate.

9. A material as claimed in claim 1 wherein said hydrated acetic acid salt is zinc acetate dihydrate.

10. A material as claimed in claim 1 wherein said hydrated acetic acid salt is cadmium acetate dihydrate.

11. A material as claimed in claim 1 wherein the silver halide developing agent is selected from the group consisting of unsubstituted dihydroxybenzene, unsubstituted trihydroxybenzene and halogen substituted, lower alkyl (C substituted, and aryl substituted dihydroxybenzenes, and l-phenyl-3-pyrazolidone.

12. A material as claimed in claim 11 wherein a silver halide developing agent is hydroquinone.

13. A material as claimed in claim 11 wherein a silver halide developing agent is monochlorohydroquinone.

5 6 14. A material as claimed in claim 11 wherein a silver 3,220,846 11/ 1965 Tinker et al. 9695 halide developing agent is monomethylhydroquinone. 3,248,219 4/1966 Jacobs.

15. A material as claimed in claim 11 wherein a silver 3,260,598 7/1966 Yutzy et al 9695 halide developing agent is l-phenyl-3-pyrazolidone.

16. A method for producing an image comprising pre- OTHER REFERENCES paring a heat developable light sensitive material as Jacobson et al.: Encyclopedia of Chemical Reactions, described in claim 1, exposing at least part of said matevol. VIII, 1959, p. 191. rial to light, and heating said material to a temperature at which said oxalate decomposes, thereby developing NORMAN G, TORCHIN, Primary Examiner said image.

10 References Cited M. F. KELLEY, Assistant Examiner UNITED STATES PATENTS CL 3,041,170 6/1962 Haist et al. 9695 9676, 95, 114.1

3,080,230 3/1963 Haydn etal. 9676 15 

